Treatment of skin disorders with UV light and cooling

ABSTRACT

Skin disorders such as, for example, atopic dermatitis, dyshidrosis, eczema, lichen planus, psoriasis, and vitiligo, are treated by applying high doses of ultraviolet light to diseased regions of a patient&#39;s skin. The dosage exceeds 1 MED, as determined for the particular patient and may range from about 1 MED to about 20 MED or higher. The ultraviolet light has a wavelength within the range of about 295 nanometers to about 320 nanometers. High doses of ultraviolet light are restricted to diseased tissue areas The skin can be cooled prior to and/or during exposure to UV light to minimize tissue damage resulting from exposure to the UV light. Higher doses of UV light can therefore be employed without injurious affects.

PRIORITY APPLICATION

This application is a continuation of U.S. patent application Ser. No.10/090,096 filed Feb. 27, 2002 and entitled “Treatment of Skin Disorderswith UV Light and Cooling”, now abandoned which claims priority under 35U.S.C. § 119(e) from U.S. Provisional Patent Application No. 60/272,277,filed Feb. 28. 2001 and entitled “Controlled Dose Delivery ofUltraviolet Light for Treating Skin Disorders” and which is aContinuation-in-part of U.S. patent application Ser. No. 09/694,086,filed Oct. 20, 2000, eytitled “Controlled Dose Delivery of UltravioletLight for Treating Skin Disorders” now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates a method and apparatus for treating skin disorderssuch as psoriasis, and more specifically, to a method and apparatus fortreating skin disorders involving exposing a patient's skin to highintensity ultraviolet (UV) light.

2. Description of the Related Art

Skin disorders, including atopic dermatitis, dyshidrosis, eczema, lichenplanus, psoriasis, and vitiligo, are conditions that commonly affectlarge populations at some time in their lives. For example, about 2% to3% of the population of northern Europe is estimated to be afflictedwith psoriasis. Although the disease's prevalence in the United Statesis not as well understood, it appears that between 150,000 and 260,000new cases are diagnosed each year. This suggests that at least severalmillion people suffer from the disease in the United States.

Psoriasis can range in severity from relatively mild, with some dryingand flaking of the affected skin, to severe cases with very severeoutbreaks over large areas of the patient's body. Even very mildpsoriasis is uncomfortable and unsightly. Severe cases can be physicallyand psychologically debilitating, presenting a very serious threat tothe patient's overall health.

Although the underlying mechanisms of psoriasis are not yet perfectlyunderstood, the disease involves abnormally rapid cell proliferation inthe basal layer of the skin. This hyperproliferation can be reduced andthe disease ameliorated with what is conventionally known as“phototherapy,” i.e., by exposing the affected skin surface to a sourceof light, in particular, ultraviolet light. Phototherapy can beperformed simply by exposing the patient to natural sunlight, or in amore controlled way by applying light from an artificial source to theaffected areas.

Commonly, a patient may be exposed over substantially his or her entirebody, or at least a very large portion of it, to artificial light froman electric lamp or a similar source generating light having asignificant ultraviolet component. While this mode of treatment has beeneffective, it is less than optimal. In recent times patients andphysicians have become increasingly aware of the undesirability ofunnecessary exposure to ultraviolet light. Ultraviolet light causesdamage to the skin and premature aging; it is also associated withmelanoma and skin cancer. Additionally, conventional phototherapytreatment is implemented over an extended time and requires the patientcomply to a regimen involving frequent visits to the physician beforeexperiencing even slight improvement in his or her condition. Followingsuch regimen is inconvenient to the patient as well as costly;furthermore treatment often fails due to lack of compliance to thisregimen. Thus, what is needed is a treatment for psoriasis and otherskin disorders that minimizes side effects such as the risk of melanomaand skin cancer and that effectuates a rehabilitation of disease tissueexpeditiously.

SUMMARY OF THE INVENTION

On aspect of the invention comprises an apparatus for treating diseasedskin with ultraviolet (UV) light. The apparatus comprises a source of UVlight within the range of 300 and 315 nanometers and a cooler forcooling the diseased skin.

Another aspect of the invention also comprises an apparatus for treatingdiseased skin tissue with ultraviolet UV light. This apparatus comprisesa source of high intensity ultraviolet light equal to or greater thanabout 1 minimum erythema dose (MED) in the wavelength range of betweenabout 300 and 315 nanometers having an output for emitting the UV lightand a cooler capable of cooling said diseased tissue.

Still another apparatus for treating an area of diseased epidermaltissue with ultraviolet UV light also includes a source of highintensity ultraviolet light equal to or greater than about 1 minimumerythema dose (MED) in the wavelength range of between about 300 and 315nanometers having an output for emitting the UV light. This apparatusfurther comprises a conduit positioned to receive said ultravioletlight, said conduit having an output end that emits said UV light, adelivery device that includes the output end of the conduit, and acooler in the delivery device. Preferably, the delivery device has alocalized UV output sufficiently small to illuminate a portion skin nolarger than said area of diseased epidermal tissue.

In another aspect of the invention, an apparatus for treating diseasedskin with ultraviolet (UV) light comprises a source of UV light withinthe range of 300 and 315 nanometers having a plate comprising UVtransparent cooling material with a cooler thermally contacted thereto.

In yet another aspect of the invention, an apparatus for treatingdiseased skin tissue with UV light comprises a source of UV light withinthe range of 300 and 315 nanometers having an output for emitting the UVlight, wherein the source includes at least one conduit with at leastone opening for connection to a source of coolant.

In still another aspect of the invention, a method for treating anepidermal region comprising diseased tissue includes cooling thediseased tissue and exposing the diseased tissue in the epidermal regionto a dosage of ultraviolet light equal to or greater than about 1minimum erythema dose (MED) in the wavelength range between about 300and 315 nanometers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a plot on axis of wavelength (in nanometers) andeffectiveness in arbitrary of the psoriasis action spectrum, humanerythema action spectrum, and the action spectrum for DNA damage (i.e.,carcinogeneity);

FIG. 2 shows a block diagram of a preferred embodiment for treating skindisorders;

FIG. 3 depicts a schematic view of one embodiment of the presentinvention comprising a laser source, a coupling lens, and an opticalfiber for exposing diseased skin to doses of UV-B wavelength (betweenabout 290 to 320 nanometers) light sufficient to effectively treat skindisorders like psoriasis;

FIG. 4 is a schematic view of one embodiment of the present inventioncomprising an arc lamp, a reflector, a wavelength selection filter, andan optical fiber for treating skin disorders;

FIG. 5 depicts a schematic view of one embodiment of the presentinvention comprising a plurality of fluorescent lamps, a reflector, anda filter for directing UV-B wavelength light to the diseased skin;

FIG. 6 shows one example of a laser system employed to direct UV-Bwavelength light of sufficient energy to effectively treat skindisorders like psoriasis;

FIG. 7 shows a delivery device that forms a part of the apparatusdepicted in FIG. 1;

FIG. 8 is an exploded view depicting internal views of the deliverydevice of FIG. 2;

FIG. 9 is an exploded view showing parts of the delivery device shown inFIG. 3;

FIG. 10 is an end view showing a delivery end of the delivery device ofFIG. 2;

FIG. 11 depicts a control panel used to control the apparatus of FIG. 1;

FIG. 12 shows a minimum erythema dose (MED) template usable with theapparatus of FIG. 1;

FIG. 13 depicts ink being applied to the delivery device of FIG. 2 by anink pad;

FIG. 14 illustrates how the delivery may be used to deliver therapy in a“tile mode”;

FIG. 15 shows how the delivery device may be used to deliver therapy ina “paint mode.”

FIG. 16 shows a delivery device that additionally includes a plate and athermoelectric cooler attached to the plate to provide cooling thereto;

FIGS. 17 and 18 are front and cross-sectional views of the chilled plateof FIG. 16; and

FIG. 19 depicts a delivery device that includes a jet that providescooling.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Deleterious effects of various skin disorders including atopicdermatitis, dyshidrosis, eczema, lichen planus, psoriasis, and vitiligocan be ameliorated by directing high doses of ultraviolet light ontoareas of skin affected by the disorder. The effectiveness of thistechnique utilizing ultraviolet light depends in part on wavelength,dosage, and what region of skin is exposed to the ultraviolet light.

Light within a specific range of wavelengths has been determined to beboth effective in rehabilitating diseased skin and also in avoidingharmful side effects such as cancer and erythema (i.e., sunburn). Thiswavelength range coincides with a spectrum conventionally known as UV-B,which extends in wavelength from approximately 280 or 290 toapproximately 315 or 320 nanometers. The wavelength of light that ismost successful at treating affected skin areas without causing harmfulside effects is defined with reference to action curves 1000, 1002, 1004for psoriasis, for erythema and for carcinogeneity, which are shown inFIG. 1. Psoriasis afflicted tissue can be effectively rehabilitated withlight having wavelengths between approximately 300 to 310 nanometers. Asshown by the psoriasis action spectrum curve 1000, light having awavelength spectrum between about 295 or 300 and about 320 or 325nanometers can be effective in healing the tissue as well, but to alesser extent. Incidence of erythema and skin cancer; as shown by therespective action spectrum curves 1002, 1004, however, increases ingeneral for shorter wavelengths in this range between 295 and 325nanometers. Risk of skin cancer, for example, is significantly higherfor wavelengths at and below about 295 to about 300 nanometers than forwavelengths above this range. Erythema is also more readily produced bylight having a wavelength of 290 nanometers than light between about 300to 310 nanometers in wavelength. Therefore, to provide optimal treatmentpreferably diseased skin on a patient is exposed to light havingwavelength that maximizes a likelihood of healing of diseased tissue yetminimizes risk of erythema and DNA damage, i.e., cancer. Accordingly,light ranging, for example, between about 295 to about 315 or 320nanometers and more specifically, between about 300 to about 310nanometers is preferred.

High, not low doses of light within these preferred ranges of wavelengthhave been determined to be most desirable. Diseased skin exposed to highdoses of light heals quicker, that is, a fewer number of high dosetreatments are required in comparison to conventional, low dosephototherapy treatments. Significant advantages derive from reduction innumber of treatments. Since less treatments are necessary for high dosetreatments, the total quantity of UV-B light to which skin is exposed toachieve healing is substantially smaller than for low dose treatments.This dosage can be quantified in total number of photons, or in totalamount of energy such as in units of Joules. For example, preferably atleast about 500 milliwatts (mW) of light having a wavelength of betweenabout 304 and about 310 nanometers is directed onto the diseased tissue.It is well known that the risk of cancer and skin damage depends on thetotal number of photons or amount of UV-B radiation directed on theskin. Thus, by raising the dosage in a single treatment and therebyreducing the number of treatments, the overall UV light exposure andthus the risk of cancer and other skin damage is lowered. Additionally,lower number of treatments may also provide a higher degree ofcompliance of a patient to an otherwise difficult regimen involving asignificant number of visits to the physician. Such a simplification intreatment is favorable as patients are less willing or able to adhere toa regimen involving multiple treatments per week for months.

In light of the foregoing reasons, doses as high as a patient cantolerate are preferred. More particularly, dosages at least as high as 1minimum erythema dose (MED) have proven to be extremely advantageous. Asdefined herein a minimum erythema dose or MED corresponds to the minimaldosage at which a noticeable change in color occurs with distinct edges.The amount of energy necessary to induce redness varies from patient topatient and depends on many factors including race, age, and skin color.Consequently, in treating a particular patient, a level of localizedexposure equivalent to 1 MED can be determined for the patient. Thislevel of exposure may be characterized by fluency or the amount ofenergy delivered to a defined area in, e.g., Joule/cm². Diseased tissueis thereby exposed to doses at least as high as that dose that creates achange in color bounded by distinct edges on healthy skin is applied.Exposure of 1 MED or higher, i.e., doses of about 2 to about 4 or evento about 6 or 8 MED are effective in remedying the diseased condition.Moreover, a direct correlation has been also observed between occurrenceof blisters and particularly successful treatments. For example, levelsof exposure to UV radiation as high as 16 to 20 MED, cause UV radiationburns that produce blisters on the skin. However, only a singletreatment at this exposure level is necessary to rehabilitate thediseased tissue. Thus, employing dosages that cause UV radiation burnsaccompanied by blistering appear to yield successful single treatmentphototherapy. For these dosage levels, however, the patient mustnecessarily be able to endure the blistering.

Although the amount of energy that corresponds to 1 MED depends on theskin characteristics of the specific patient, for effective treatment ofskin disorders like psoriasis, the recommended fluency of light havingwavelengths distributed between about 300 and about 310 nanometers hasbeen determined to range between about 10 milliJoule/square centimeter(mJ/cm²) to about 4.0 Joule/square centimeter (J/cm²). Morespecifically, the range of fluency preferably ranges between about 100mJ/cm² to about 1.8 J/cm², and more preferably between about 600 mJ/cm²and about 1.2 J/cm². Accordingly, doses as high as 500 mJ/cm², 1 J/cm²,and 1.5 J/cm² of light having wavelengths at least as large as 300nanometers but less than or equal to about 310 nanometers may beemployed to treat skin disorders. Less doses of shorter wavelength lightare required in comparison to longer wavelength of light. For example,fluencies in a range of about 50 mJ/cm² to about 1 J/cm² of light with acenter wavelength of about 305 nanometer (e.g. between 304.5 and 305.5)may produce similar results as fluencies ranging from about 300 mJ/cm²to about 4 J/cm² of light having a wavelength centered about 310nanometers (e.g., between 309.5 and 310.5). The action spectrum forerythema 1004 dictates in part how the required dose varies withwavelengths. As shown in the action spectrum 1004 depicted in FIG. 1,erythema is more readily induced by shorter wavelengths than longerwavelengths. In particular, the erythema response is about ten timesstronger for light having wavelength centered about 305 nanometers(e.g., between 304.5 and 305.5) than for light centered about 310nanometers (e.g., between 309.5 and 310.5). (Note that effectiveness asplotted in FIG. 1 corresponds to the degree the tissue is affected byone joule of optical energy.)

Since high doses of ultraviolet light enhance the risk of skin cancerand erythema as well as cause other skin damage generally associatedwith premature aging, the extent of a patient's epidermis to which lightis directed must be limited. Since the diseased tissue needs to beexposed, light is not delivered to regions of skin other than affectedareas, which particularly with psoriasis, are more tolerant to higherdoses of light within the preferred wavelength regions than is healthytissue. In treating psoriasis, for example, the UV light is preferablydirected onto the lesional as well as surrounding paralesional tissue,which although appearing normal is diseased tissue. Treatment, however,should be restricted only to these affected areas of skin, and areasuninvolved are preferably not exposed to the ultraviolet light.Certainly, the patients entire body is not subjected to the ultravioletlight as is true in some conventional phototherapy treatments. Instead,the ultraviolet light must be delivered to each separate affected regionof the body. By avoiding treatment of unaffected portions of skin, thedosage can be raised well above conventional dosages as the affectedareas will tolerate substantially higher doses without increased risk ofside effects. Accordingly, the high doses of UV illumination aredirected to an area on the skin that is preferably less than about 3000cm², more preferably less than about 1000 cm², and most preferably lessthan about 500 cm².

The temporal extent over which exposure occurs is also important.Exposure of the affected area to the UV light results in heating of thetissue. Unless this heat is sufficiently dissipated, thermal blisteringwill result. In particular, blisters are formed if the temperature ofthe skin is raised to about 50° C. Thermal energy absorbed by theexposed portion of skin, which may reach a depth between about 5 and 100micrometers (μm), must be conducted away from that region before itheats up the skin to excess. Specifically, the region should not heat upto the critical temperature of about 50° C. or more which would resultin the formation of thermal blisters. Whether the thermal energy issufficiently dissipated depends in part on the thermal time constantτ_(THERMAL) of the skin, which governs the rate of heat dissipation. Therate at which thermal energy is introduced into the skin is also arelevant factor. Preferably, therefore, the high dose of energy providedby the UV light is distributed over a length of time greater than one ortwo times the thermal time constant associated with the removal of heatfrom the tissue. This duration of exposure may for example range betweenabout 500 milliseconds (msec) and 1500 milliseconds for radiationdelivered at 308 nanometers at fluences of less than 1 W/cm². Theillumination needs to be within a short enough time to be practical yetlong enough to prevent blistering cause by thermal overload.

An excimer laser can generate short high power pulses of light having awavelength of about 308 nanometers. These pulses can be high in power,e.g. about a half a million watts, but short in duration, for example,maybe lasting much less than 100 nanoseconds (e.g., 30 nanoseconds). Thelaser, however, may produce a plurality of such pulses at a repetitionrate of about 200 Hz, i.e., one pulse per 5 milliseconds. Tissue exposedto a plurality of these short pulses will increase in temperatureslightly with application of each pulse. The cumulative effect of theplurality of pulses being to raise the temperature of the tissue anamount that depends in part on the heat capacity of the tissue. The heatcapacity is directly related to the thermal time constant τ_(THERMAL) ofthe skin described above, which governs the rate of heat dissipation ofheat from the skin after the series of pulses is complete. Preferably,therefore, the energy from the laser is spread over a long enough periodof time with respect to the length of the thermal time constantτ_(THERMAL) so as to permit sufficient dissipation to avoid excessivebuild-up of heat from the plurality of short pulses. Thermal damagecaused by raising the temperature of the skin above, for example, theblister temperature of 50° C., can thereby be prevented. The amount oftime required to expose the affected tissue to the therapeutic doses ofUV light, however, depends on the particular dose level.

This phototherapy treatment can be accomplished by utilizing anapparatus 1010 comprising an ultraviolet light source 1012 and adelivery system 1014 such as illustrated in block diagram form in FIG.2. The ultraviolet source 1012 may comprise a laser, a lamp, or asolid-state device such as a light emitting diode. One or more of suchlight sources 1012 may be used alone or in combination with othersimilar or different light sources to produce light of sufficientintensity and at the appropriate wavelength to treat the skin disease.An excimer laser, and more specifically, a XeCl gas laser outputtinglight having a wavelength of about 308 nanometers, or an arc lamp orfluorescent lamp that provides radiation within the UV-B region areparticularly suitable light sources for this application. A filter maybe included to remove light outside the preferred wavelength ranges.This filter may comprise a dichroic or dielectric filter or a grating.

The delivery system 1014 may comprise a hand device that can be readilyhandled and moved to direct light onto the affected areas skin.Alternately, the delivery system 1014 may comprise a scanner possiblycomputer controlled, such as one that utilizes mirrors or reflectivesurfaces that move and thereby translate a beam of ultraviolet lightextracted from the light source. A spatial light modulator, an opticalcomponent having a surface comprising a plurality of smaller regionseach of which can independently be set to either transmit or block aportion of light incident on the surface of the modulator, may also beemployed to appropriately distribute the ultraviolet light onto thepatient's skin. Such spatial light modulators as are currentlyavailable, as well as those yet devised, include ones that switchmechanically, and ones that accomplish switching by altering thepolarization of light passing therethrough.

The delivery system 1014 must be adapted to deliver the high dose to atarget region of skin spanning between about 300 to 700 cm² or morepreferably between about 400 and 650 cm². Accordingly, the deliverysystem 1014 may include a focusing element such as a lens or mirror forfocusing the optical beam down to a small region. Alternatively, thedelivery system 1014 may have an aperture for egress of the UV light tolimit beam size. For example, this aperture may be a square aperturewith sides that restrict the size of the beam. An optical path 1016provided for example by an optical waveguide may channel light from thelight source 1012 to the delivery system 1014. This optical waveguidemay comprise an optical fiber bundle including a plurality of fibercomprising material transparent to UV-B radiation such as quartz orfused silica. The optical fiber line 1016 may include a liquid filledoptical guide such as shown in U.S. Pat. No. 4,927,231 issued to JeffreyI. Levatter on May 22, 1990, which is incorporated herein by reference.This liquid filled optical guide is especially suited to transfer largeamounts of optical power. The power-handling capability of the opticalcomponents within the apparatus 1010 are particularly important giventhat doses of 1 MED or higher are being applied to the patients skin.

In particular, the ultraviolet light source 1012 and the delivery system1014 as well as the optical path 1016 need to handle power levels highenough to provide therapeutic doses of 1 MED or more. The prolongedduration over which the skin is exposed to the UV light, however,mitigates against the necessity for excessively high power requirementsfor these and other components in the apparatus 1010. As discussedabove, the energy density delivered to the patient is preferably in arange of about 205 to about 1200 mJ/cm². However, to avoid blistering,the dosing with UV light is extended over a sufficiently long period oftime so as to permit the thermal energy to be adequately dissipated. Thepower is optionally transported by a waveguide or with the aid of anyother optical element and delivered by the delivery system 1014. Otheroptical components such as lenses, mirrors, filters, grating etc. in theoptical path of the UV light directed onto the patient must also beadapted to handle the levels of power sufficient for successfultreatment of the patient.

As discussed above, the apparatus 1010 must be adapted to provide dosesof UV light over short intervals, e.g., between about 0.5 and 1.5 sec induration. Such periodic dosing can be provided by including a switch, amodulator, or a shutter within the path of the beam of UV light. Forexample, electro-optical and acousto-optical modulators, electro-opticaland magneto-optical switches, as well as other optical devices thatdeflect, block, or otherwise interrupt the UV light output from theapparatus can be employed to prevent UV light from reaching theepidermis of the patient. Other alternatives include switching the lightsource on and off. Optical output from a solid state device such as alaser diode or a light emitting diode can be electrically controlled;accordingly such UV light sources 1012 can be intermittently activatedso as to expose the patient over brief intervals. As discussed above,some light sources inherently produces pulsed output. Short pulses oflight, for example, are emitted from pulsed lasers or pulsed lamps.Pulsed lasers and lamps that produce UV light are particularly suitableUV light sources. Other UV sources as well as other methods that yieldshort pulses of UV light for dosing a patient may also be appropriatefor use in conjunction with the apparatus.

As discussed above and shown in FIG. 3, the UV light source 1012 maycomprise a laser 1020 such as an excimer laser. Preferably, the laser1020 comprises a XeCl laser that emits light having a wavelengthcentered about 308 nanometers. Like lasers well known in the art, thelaser 1020 includes a gain medium (not shown), e.g. gaseous XeCl,surrounded by two mirrors (not shown), one substantially entirelyreflective and the other that is partially transmissive. One end 1022 ofan optical line 1024 comprising a waveguide in the form of for example asingle optical fiber, an optical fiber bundle or a light pipe, isjuxtaposed proximal to the partially transmissive mirror, another distalend 1026 of the optical line 1024 being attached to a delivery device1028 comprising a hand piece 1030. A coupling lens 1032 is insertedbetween the partially transmissive mirror and the optical guide line1024. The handpiece 1030 also includes a lens 1034.

Light emitted by the laser 1020 is coupled into the optical line 1024via the coupling lens 1032. This light propagates through the opticalline 1024 substantially without absorptive loss and on into thehandpiece 1030, which can be manipulated by the user to direct the UVlight onto the portion of the patient's epidermis designated fortreatment. The lens 1034 within the handpiece 1030 focuses the UV lightonto a small region 1036, one for example between about 1 and 4 cm² insize.

In one embodiment, proximal end 1022 the optical line 1024 may have ancircular cross-section 1038 while the distal end 1026 has a square orrectangular cross-section 1039. The lens 1034 in the handpiece 1030,preferably comprising fused silica, images the square or rectangularlyshape distal end 1039 of the optical line 1024 onto the skin of thepatient. Accordingly, the region of the skin that is illuminatedcomprises an area having a square or rectangular shape. The irradiancemay be uniform over this square or rectangular area 1036 so as to enablethe user to provide a uniform dose to a large area of diseased skin(i.e., larger than the image of the distal end 1026 of the optical line1024) by employing two methods described below that are herein referredto respectively as the paint and tile methods.

Utilizing a fiber bundle comprising a plurality of fibers as the opticalline 1024 is preferable because the coupling lens 1032 cannot focus theUV light down to an area small enough for coupling the light into asingle fiber having a small cross-section. In particular, thecross-section of the single fiber will be smaller than the cross-sectionof the beam even after focusing via the coupling lens 1032. The lightcollected from the UV light source 1012 cannot be efficientlytransferred into the single fiber and the amount of light that iscoupled into the fiber is inadequate to provide an effective andreasonable treatment for skin disorders. The amount of energy that canbe injected into the fiber, as well as into a optical fiber bundle, isequal to the product of the radiance from the light source 1012, thecross-section of the fiber or fiber bundle where the light enters andthe numerical aperture of the optical fiber or optical fiber bundle.Since conventional fused silica fibers generally have a numericalaperture of about 0.22, the cross-section of the fiber (or the fiberbundle) is the parameter that can be altered. In particular, thiscross-section preferably has an area large enough to receive the entirefocused beam from the coupling lens 1032.

A fiber bundle is further advantageous, because it can offer a methodfor converting a beam profile having a circular cross-section, to onehaving a square or rectangular cross-section. The proximal end 1022 ofthe fiber bundle can be configured into a circular geometry, i.e., onehaving a circular cross-section, while the output end can be shaped intoa square geometry with a square cross-section. This arrangementeliminates the need for a specialized optical component such as aspecialized light pipe in the handpiece 1030 to act as a diffuser and/orbeam shaper thereby reducing the weight and cost of manufacture of thehandpiece and at the same time increasing its resistance to damage whendropped.

As discussed above, preferably, the laser 1020 is a pulsed laser. Morepreferably, the laser 1020 is an excimer laser such as a XeCl excimerlaser and outputs light having a wavelength of about 308 nm.Alternatively the laser 1020 may comprise a solid state laser or a dyelaser and may be supplemented with wavelength selective device such asone or more filters, gratings, or prisms. These filters may includedichroic or interference filters and may comprise dielectric or metallayers. The wavelength may also be controlled using optical componentsexploiting non-linear optical properties.

Additionally, the laser UV light source 1020 as employed for theabove-described dermatological applications necessitate that certainperformance requirements be satisfied. In particular, to be commerciallysuccessful, the apparatus 1010 preferably can operate for at least aboutone to three months without requiring servicing, a period during which,on average, a physician may treat between about 100 to about 300patients. Treatment of a single patient may often involve dosingaffected tissue, which altogether spans a large portion (e.g., 20percent) of the patient's entire body, each individual dose, however,being administered over a localized region 1036 of skin, e.g., 1 cm² fora period in excess of the thermal time constant. Since UV light must beseparately applied to potentially a large number of different sites onthe epidermis, the laser needs to be activated for extended periods oftime, e.g., between about 1 to 2 hours total for a single patient, andfor between about 100 to about 600 hours for 200 patients over the threemonth period. Thus, the laser being employed for dermatologicalapplications such as the treatment of psoriasis, atopic dermatitis,dyshidrosis, eczema, lichen planus, and vitiligo must have asufficiently long lifetime so to offer a practical cost effectivesolution for handling such medical conditions.

In the case when the laser light source 1020 for these dermatologicalapplications is an excimer laser, selecting the proper materials to beemployed in constructing of the laser are critical. A suitable gasexcimer laser such as an XeCl laser, for example, may comprise pressurevessel that contains a halogen gas, first and second electrodes forcreating a laser discharge between the electrodes and generating a laserbeam between first and second optical components, a fan for circulatingthe gases, and a heat exchanger for cooling the gas. By utilizingspecific materials in fabricating the pressure vessel, the electrodes,the heat exchanger and the fan of the laser, its lifetime can beextended beyond 3600 hours. The criteria for selecting the appropriatematerials for the laser can be found in U.S. Pat. No. 4,891,818 issuedto Jeffrey I. Levatter on Jan. 2, 1990, which incorporate herein byreference. In particular, portions of the pressure vessel, first andsecond electrodes, fan and heat exchanger that are in contact with thehalogen gas are fabricated entirely of a material that reacts with thehalogen gas to form stable reaction products having a vapor pressure ofless than 10⁻⁶ torr at normal operating temperatures. According, thecontamination of the gas by the pressure vessel, first and secondelectrodes, heat exchange, and fan is minimized and the lifetime of theexcimer laser is increased. Electrically-conductive portions of thepressure vessel, first and second electrodes, fan and that exchangerthat are exposed to the halogen gas may be formed of alumina, e.g. highpurity alumina, while non-electrically-conductive portions of thepressure vessel, first and second electrodes, fan and that exchangerthat are exposed to the halogen gas are formed of nickel, e.g., highpurity nickel, stainless steel or aluminum, e.g., polished aluminum orpolished stainless steel. By utilizing these types of materials thatreacts with the halogen gas to form stable reaction products having avapor pressure of less than 10⁻⁶ torr at normal operating temperatures,an excimer laser light source can be realized that is suitable fordermatological applications, i.e., that can withstand extensive usageover an extended period of time of from about one to three months.

As discussed above and shown in FIG. 4, the light source 1012 maycomprise a lamp 1040, in particular an arc lamp, such as a mercury arclamp, like Model No. 69175 made by Osram Sylvania Products Inc., 275West Main Street, Hillsboro, N.H. 03244. Other lamps 1040 that produceultraviolet radiation in the range of between about 302 to 310nanometers include germicidal lamps available from Philips Lighting Co.,200 Franklin Square Drive, Somerset, N.J. 08875, deuterium arc lamps,which emit much of their energy below 300 nanometers and requireadditional filtering, and metal halide lamps, e.g., those available fromFusion UV Systems Inc., 910 Clapper Road, Gaithersburg, Md. 20878.Another alternative includes zirconium arc lamps available from OsramSylvania Products Inc., which emit substantial amounts of energy in the302 to 310 region of the electromagnetic spectrum from a small volume.

In the apparatus 1010 shown, a reflector 1042 having a reflectivesurface 1044 is located on one side of the arc lamp 1040. The reflector1042 may have a spherically, parabolically, or ellipsoidally curvedsurface 1044 that is reflective for UV wavelengths of light preferablybetween about 300 to about 315 nanometers and that has an optical axiswhich passes through the arc lamp 1040.

On an other side of the lamp 1040 is a UV filter 1046 such as aninterference or dichroic Filter followed by a focusing lens 1048 anddelivery device 1014 that includes an optical fiber bundle 1050.Preferably, the filter 1046, focusing lens 1048, and fiber bundle 1050are located on the optic axis of the reflector 1042. Note that in placeof the reflector 1042, a lens (not shown) comprising e.g., fused silica,can be employed to collect light from the arc lamp 1040 and instead ofthe filter 1046, a prism or grating may be utilized for wavelengthselection. For example, two passes through a diffraction grating inseries can be used to select a narrow bandpass at any location on thelamp emission spectrum with the advantage of being wavelength-stableover broad operating temperature ranges and over production numerousruns. Alternatively, two identical 302 nanometer dielectric filtersstacked consecutively may narrow the spectrum; however dielectricfilters operating near their cut-on edge are sensitive to changes intemperature and also vary from one production run to another.

The delivery device 1014 may comprise a handpiece 1052 which has anoutput tip 1054 and that contains the optical fiber bundle 1050. Adisposable or steralizable tip 1056 may prevent the output tip 1054 fromcontacting the patient. The fiber bundle 1050 may comprise silica,quartz, or a liquid filled fiber optic. The fiber bundle 1050 has oneend 1058 which may serve as the output tip 1054 of the handpiece 1052 ormay be imaged and/or focused onto the patient with another lens (notshown) in the handpiece. This end 1058 of the fiber bundle 1050 may besquare or rectangular so as to produce a square or rectangular beamprofile that is directed onto the patient in order to facilitateadministration by the physician or health care provided a uniformcoverage over the affected tissue.

Light from the arc lamp 1040 is collected by the reflector 1042 whosecurved reflective surface 1044 is preferably dichroic and reflectspredominantly light having wavelengths between about 300 to about 315nanometers or 300 and 310 nanometers. Light from the arc lamp 1040radiates toward the reflective surface 1044, reflects therefrom andthrough the dichroic filter 1046. A portion of the light is alsoradiated from the arc lamp 1040 and toward the filter 1046 directly.This radiation also passes through and is filtered by the dichroicfilter 1046. Radiation from the arc lamp 1040 that is transmittedthrough the filter 1046 reaches the focusing lens 1048 which couples itinto the optical fiber bundle 1050 where it exits therefrom at theoutput tip 1054 of the handpiece 1052. This light is directed onto thepatient. Preferably, the lamp 1040 outputs sufficient power such thatafter losses within the apparatus 1010, approximately 0.5 to 2.0 W ofpower exits from the handpiece 1052 and is directed onto the patient.

The optical filter 1046 or filters are used to restrict treatment to aband between about 300 and 315 nanometers. Lamp energy below 300nanometers is strongly rejected by the optical filter(s) 1046 to preventerythemal burning and/or carcinogenic effects. Lamp energy above 315nanometers induces a sensation of heating and is also removed byfiltering to ensure patient comfort. Employing broadband light, such asfor example that includes wavelengths between about 300 and 315nanometers, as opposed to using a single intense spectral line, e.g. the312 nanometer line, captures a substantial percentage of the UV energyemitted by the arc lamp. Limiting treatment to only a single narrow linesuch as the 312 nanometer line is not preferred as the phototherapyresponse to this line is nearly twenty times less than the response forlight having a wavelength of 302 nanometers. Advantageously, a spectralband of between about 302 to 315 nanometers exploits the higherphototherapy response of the shorter wavelengths such as between about302 and 305 nanometers as well as the higher spectral emittance obtainedfor wavelengths ranging between about 305 and 315 nanometers. Theapparatus 1010 with a mercury arc lamp, for example, therefore has thepotential of treating a much larger area of skin in the same amount oftime as an XeCl laser if large lamps or efficient optical collectors areemployed.

As depicted in FIG. 5, the light source 1012 may comprise a bank orgroup 1070 of small fluorescent lamps 1072 such as the Philips CLEOcompact lamp or the Phillips TL 40W/10R, which emits a moderate amountof energy in the range of between 300 and 310 nanometers; both lamps areavailable from Philips. The bank 1070 of fluorescent lamps 1072 issandwiched between a reflector 1074 located on one side and a lens 1076,here, a fresnel lens located on an opposite side of the lamps. Thereflector 1074 comprises a plurality of curved reflective surfaces 1078,one associated with each of the fluorescent lamps 1072 in the bank 1070.These curved reflective surface 1078 may have cross-sections that form asegment of a circle, a parabola or an ellipse. Adjacent the fresnel lens1076 is an wavelength selective filter 1080 followed by another lens1082, here a small refractive lens having sufficient power and beingproperly, positioned so as to provide focusing. An optical fiber bundle1084 with an output tip 1086 is also included in the apparatus 1010.

Ultraviolet radiation from the lamps 1072 is collected by the reflector1074 and the fresnel lens 1076 and passes through a wavelength selectivefilter 1080. The filtered light is focused onto one end 1088 of theoptical fiber bundle 1084 by the focusing lens 1082 and is transmittedthrough the length of the fiber bundle and exits from the output tip1086 of the fiber. The apparatus 1010 may be made quite small byemploying small fluorescent bulbs 1072. If the apparatus 1010 issufficiently small and lightweight, the fiber optic bundle 1084 can beeliminated and the apparatus 1010 can be aimed or scanned by the userover the patient's affective areas of skin.

Moreover, although each of the systems 1010 described above and depictedin FIGS. 3-5 may include optical fiber bundles, as indicated, thesystems are not so limited. For example, single or plural optical fibersor light pipes and/or other waveguide devices can be employed.Alternatively, the UV light may propagate in free space over a pathwhich may or may not be manipulated by optical elements located in thatpath.

EXAMPLE

Another example of an apparatus 10 suitable for deliveringelectromagnetic energy to treat a skin condition in a medical patient isdepicted in FIG. 6. The apparatus 10 comprises an ultraviolet lightsource 12 and a delivery device 15. A cable 17 connects the deliverydevice 15 to the UV light source 12 so that energy from the UV lightsource can be delivered through the delivery device to the skin of amedical patient. The apparatus 10 is powered from an external electricalpower source through a suitable electrical cable (not shown), whichplugs into a typical, grounded wall socket.

In a preferred embodiment, the UV light source 12 is a 308 nanometerXeCl excimer laser. The 308 nanometer energy output is within the UVBrange (i.e., about 290 to 320 nanometers) of ultraviolet light which, asdescribed above, is therapeutically useful in the treatment ofpsoriasis. This generator 12 produces ultraviolet light pulses with anenergy content of about 15 millijoules per pulse. Individual pulses havea duration; of about 30 nanoseconds (full width at half maximumintensity) and the pulses are repeatable at frequencies between about100 and 150 Hertz.

The UV light source 12 is contained inside a housing 20 with a front 21and bottom 22. One or more fans (not shown) assist in cooling theexcimer laser by forcing air through air vents 23 on the exterior of thehousing 20. The UV light source 12 is movable on wheels or casters 25 onthe bottom 22 of the housing 20. Handles 27 on the front 21 of thehousing assist in moving the UV light source 12. A control panel 30 onthe front 21 of the housing 20 allows a user of the system 10 to set andadjusts the operating parameters of the UV light source 12. Operation ofthe system 10 is controlled by a user by means of a foot pedal 31, whichcan be placed on the floor adjacent the UV light source 12 and which iselectrically coupled to the light source 12 by means of a foot pedalcable 34. Operation of the system 12 to deliver therapy to a patient isdescribed more fully below.

The delivery device 15 comprises a hand-held wand 32. This wand 32 isoptically coupled to the UV light source 12 by means of the cable 17,which includes a fiber optic delivery cable 33 configured to conductultraviolet light emitted by the excimer laser down the cable to thewand. The optical fiber cable 33 in the cable 17 connect to the UV lightsource 12 at an output connection 35 on the face 21 of the housing 20. Asecond return fiber optic cable 38 connects to a return connection 40 onthe housing 20 in the vicinity of the output connection 35. Acalibration port 42 is also disposed on the front face 36 of the housing20 and is sized to receive the wand 32 therein.

Exterior details of the hand-held wand 32 are shown in FIG. 7. The wand32 comprises an elongate, generally cylindrical body member 45 thatincludes a connecting end 48 and a delivery end 50. A clear plasticcylindrical shield 53 is insertable into the delivery end 50 of thewand. The end of the shield 53 opposite the body 45 of the wand 32includes positioning nubs 55, which are intended to bear against thepatient's skin as energy is being delivered to the patient. The use andfunction of the positioning nubs 55 are described in more detail below.Preferably, the shield 53 is removable from the wand 32 and disposable,or at least conveniently sterilizable, so that the wand itself isreusable indefinitely between multiple patients.

Still referring to FIG. 7, the delivery cable 33 and return cable 38connect to the connecting end 48 of the wand 32. The cables 33, 38connect to the wand 32 through a pair of elastomeric connection boots57, which provide strain relief and guard against kinking of thedelivery and return cables. A switch in the form of a pushbutton 60selectively allows or prevents the emission of ultraviolet energy fromthe delivery end 50 of the wand 32. The structure, function, andoperation of the pushbutton 60 are described in more detail below inconnection with FIG. 8.

FIG. 8 is an exploded view showing the constituent parts of thepreferred embodiment of the wand 32 through which ultraviolet energy maybe delivered to the skin of the medical patient. The wand 32 comprises amain body member 62 and a secondary body member 65. The two body members62, 65 are held together by screws 68. A spacer 70 maintains anappropriate separation between the main and secondary body members 62,65 near the connecting end 48 of the wand 32.

A fiber optic delivery line 73 connects to the connecting end 48 of thewand 32 through one of the connection boots 57. The fiber optic deliveryline 73 is coupled to a fiber optic delivery connector 75, whichconnects to a fiber optic delivery adaptor 77, which is in turn screwedinto a fiber optic delivery port 80 at the connecting end 48 of the wand32. These components direct ultraviolet energy from the UV light source12 (see FIG. 6) and into the wand 32. The ultraviolet energy travelsthrough the wand 32 through a first light pipe or fiber bundle 82 to ashutter assembly 85, the construction and functioning of which will bedescribed in more detail below.

A second light pipe or waveguide 88 runs inside the wand 32 parallel andadjacent to the first light pipe or waveguide 82. The second light pipeor waveguide 88 is optically aligned with a fiber optic return line 90,which connects to the connecting end 48 of the wand 32 through fiberoptic return adaptor 93 and a fiber optic return connector 95. The fiberoptic return line 90 is routed through a connection boot 57 and returnsback to connect to the return connection 40 on the face of the UV lightsource 12 (see FIG. 6).

The second pipe or waveguide 88 may be narrower than the first lightpipe or waveguide 82 because, while the first light pipe or waveguidemust be of sufficient diameter to transmit ultraviolet energy ofconsiderable power for effective treatment, the second light pipe orwaveguide only transmits a very small amount of energy reflected fromthe patient's skin back to a detector (not shown) inside the UV lightsource 12 (see FIG. 6). While energy is being transmitted, energy willbe reflected from the patient's skin and detected by the detector.Failure of the detector to detect energy reflected from the patient'sskin during energy delivery will most likely indicate a blockage alongthe light path or some other problem with the delivery or generationsystem. In that case, the equipment will cease energy delivery and anerror message will be delivered to the operator.

During energy transmission, ultraviolet energy from the generator 12travels through the wand 32 to a shutter assembly 85 inside the wand.Details of the shutter assembly 85 are shown in FIG. 9. The assemblycomprises a shutter plate 96, which includes structure defining arelatively large delivery aperture 97, and a relatively smaller returnaperture 100. An upper tab 103 at the top of the shutter plate 96 fitsinto a slot (not shown) in the underside 105 of the pushbutton 60. Ashutter plate pin 107 holds the upper tab of the shutter plate 96 inplace in the slot of the pushbutton. A compression spring 110 is fittedonto a spring post 112 on the underside of the pushbutton.

The operation of the shutter assembly 85 can best be appreciated byreferring once again to FIG. 8, in which the shutter assembly is shownin relation to the other components of the wand 32. A lower tab 115 atthe bottom of the shutter plate 96 fits into a slot 116 in a shutterplate retainer 118, which fits into a receiving space 120 within themain body member 62 of the wand 32. The shutter plate retainer 118 isheld within the receiving space 120 by a retaining rod 125 and aretaining sleeve 127, or by other suitable means. A tactile feedbackmember 130 fits within the receiving space 120 just below the shutterplate retainer 118.

When the user wants to deliver ultraviolet energy to a patient's skin,the user presses down on the pushbutton 60, thereby compression thecompression spring 110 against a shelf 132, which partially overlies thereceiving space 120 inside the main body member 62 of the wand 32. Asthe pushbutton is pressed further, the lower tab 115 on the bottom ofthe shutter plate 96 extends through the slot 116 in the shutter placeretainer and presses down against the tactile feedback member 130. Thetactile feedback member is made of spring steel or s similar suitablematerial and is configured to produce a “snap” or “click” that isreadily noticeable by the user when the pushbutton is fully depressed.

When the pushbutton 60 is fully depressed, the delivery aperture 97 andthe return aperture 100 of the shutter plate 96 will be aligned with thefirst light pipe or waveguide 82 and the second light pipe or waveguide88, respectively. A pathway is thereby created for ultraviolet energy ina therapeutic amount to travel down the first light pipe or waveguide 82and through the delivery aperture 97 towards the delivery end 50 of thewand 32. A second pathway is formed simultaneous for the return ofreflected energy from the patient, through the return aperture 100, backalong the second light pipe or waveguide 88, and ultimately back to theUV light source 12 (see FIG. 6), where the reflected energy will bedetected as a return signal by a detector (not shown) inside the UVlight source.

When the user releases the pushbutton 60, force from the compressionspring 110 returns the shutter plate 96 to a position in which theshutter plate prevents energy from the first light pipe or waveguide 82from exiting the wand 32. A second pathway is formed simultaneous forthe return of reflected energy from the patient, through the returnaperture 100, back along the second light pipe or waveguide 88, andultimately back to the UV light source 12 (see FIG. 6), where thereflected energy will be detected as a return signal by a detector (notshown) inside the UV light source.

When the user releases the pushbutton 60, force from the compressionspring 110 returns the shutter plate 96 to a position in which theshutter plate prevents energy from the first light pipe or waveguide 82from exiting the wand 32. This is a safeguard against accidental releaseof ultraviolet energy in the event of unintentional activation of the UVlight source 12. Should energy be generated inadvertently, the energywill be blocked from exiting the device 15 unless the user has depressedthe pushbutton.

When the UV light source 12 is activated with the pushbutton 60depressed, ultraviolet energy emerges as a beam from the first lightpipe or waveguide 82 and travels towards the delivery end 50 of the wand32. After the beam crosses the shutter plate 96, it enters a lens in thewand 135. From the lens 135, the beam travels through an aperture plate138, which gives the beam a square cross-section with well-defined edgessuited for delivering uniform and well-controlled therapy to thepatient. The lens 135 and aperture plate 138 are housed within an opticsshell 140 and held inside the optics shell by a retaining ring 142, withthe optics shell retained inside the wand 32 by a set screw 145.

Although the pushbutton 60 with aperture plate 138 connected theretoenables the user to further control the application of UV light from theUV light source 12, this feature is not necessary. The apparatus 10 mayrely on other arrangements for regulating the short bursts of UV lightoutput therefrom. Many types of light sources, including lasers andflash lamps, can be adapted to output optical pulses of varyingduration. Alternatively, electro-optical, magneto-optical,acousto-optical, and even all optical switches and modulators, as wellas electrically or magnetically activated mechanical modulators orshutters may be suitably employed to switch the UV output from theapparatus 10 on and off.

Referring still to FIG. 8, the cylindrical clear plastic shield 53 isinserted into the delivery end 50 of the wand 32. The shield 53 bearsagainst an edge 147, which ensures that the positioning nubs 55 on theend of the shield are at proper distance from the lens 135 inside thewand 32. Additionally, the shield 53 is keyed so that the nubs 55 arealigned with the corners of the aperture plate 138, so that the cornersof the beam impact the patient's skin substantially at the inner cornersof the nubs when the therapy is delivered to the patient. The shield 53may be keyed for proper insertion into the wand 32, e.g., by theprovision of a ridge and a corresponding slot on the wand and theshield.

Soft pads 150 are affixed to the positioning nubs 55 on the end of theplastic shield 53. The shield 53 is sized and positioned so that thecorners of the beam are positioned substantially at the nubs 55 on theclear plastic shield. To ensure that the nubs 55 are positionedaccurately, the material of the shield 53 must be a substantially rigidmaterial. The soft pads 150, which in the preferred embodiment are arelatively soft biocompatible silicone, are affixed to the nubs 55 ofthe shield 53 to enhance the patient's comfort and avoid injury wherethe shield contacts the patient's skin. The soft pads 150 also serve topick up and transfer to the patient's skin small quantities of asuitable biocompatible ink. This assists the caregiver in uniformlyapplying the ultraviolet energy in a technique that will be described inmore detail below. The soft pads 150 may be affixed to the nubs 55 witha suitable adhesive or by any other appropriate means.

FIG. 10 is a view, end-on, of the disposable shield 53 in place on thedelivery end 50 (see. FIG. 8 of the wand 32). FIG. 10 also shows theshield nubs 55 that carry the soft pads 150, as well as the apertureplate 138 that forms part of the wand optics. As noted above, the opticsof the device 15, and in particular the lens 135, are designed so thatthe energy beam emerging from the wand 32 has a square-cross sectionwhose corners coincide with the positions of the soft pads 150 on thenubs 55.

FIG. 11 is a frontal view showing details of the control panel 30 on thefront 21 of the UV light source 12 (see FIG. 3) and through which theoperator interacts with the apparatus 10. The control panel 30 includesa power indicator 153 in the form of a green lamp that is lit wheneverpower is supplied to the generator unit 12. Adjacent the power indicator153 is another green lamp that serves as a ready indicator 155, andwhich is lit when the unit is ready to deliver laser energy through thewand 32. A lasing indicator 158 in the form of an amber lightilluminates while laser energy is being generated and delivered throughthe wand 32. A large, red pushbutton serves as an emergency stop button160, which, when pressed, cuts power to the laser generator 12 therebyhalting energy delivery through the wand 32.

A display window 162 is provided with an LED or LCD display or similarmeans for communicating information to the operator of the system 10.Four entry keys 165 are provided below the display window 162. Byoperating these keys the operator. can input data into the system 10,e.g., through the use of menus and choices displayed to the operatorthrough the display window 162.

A master key switch 167 is located at the lower left corner of thecontrol panel 30. When the master key switch is off, no power issupplied to the system 10 and energy generation is disabled. Provisionof a key to control this switch 167 is a security measure to limit useof the system 10 to authorized personnel. A master key switch indicator170 is provided in the form of a green LED just above the master keyswitch 167. The master key switch indicator 170 lights whenever themaster key switch 167 is in the “ON” position.

A reset button 172 is operable to switch the system 10 into a“power-on/self-test/warm-up” (“POST”) mode. The POST mode is enteredautomatically when the system 10 is first switched on, after a powerinterruption, of when the rest button 172 is pressed. In POST mode, thesystem 10 performs diagnostic tests to assure that its components areoperating properly and warms up the laser, a process that takesapproximately three minutes. A POST mode indicator in the form of ayellow LED above the rest button 172 lights when the system 10 is inPOST mode.

A standby button 178 is located to the right of the rest button 172 onthe control panel 30. The system 10 enters a standby mode after the POSTmode is completed and the unit warmed up, when the operator presses thestandby button 178, or if two minutes elapses without energy deliverywhile the system is in any “treatment” mode, details of which aredescribed below. The standby mode is a condition in which the system 10is warmed up, operable, and ready to be switched into one of thetreatment modes. Standby mode is indicated by a standby mode indicator180 in the form of a green LED above the standby button 178.

A MED ready mode button 183 is operable to switch the system 10 in thefirst of three treatment modes, the MED mode. The MED mode is adiagnostic mode in which the system 10 is operated to determine apatient's minimal erythema does (MED). The MED mode is indicated by anMED mode indicator 185 in the form of a green LED located directly overthe MED ready mode button 183. Operation of the system 10 in MED mode isdescribed in more detail below.

A treatment ready mode button 188 is located to the right of the MEDready mode button 183. When the treatment ready mode button 188 isdepressed, the system is usable in either of two therapeutic treatmentmodes: tile mode or paint mode. Selection of tile mode or paint mode ismade by the operator with a treatment mode key switch 190 disposed justto the right of the MED ready mode button 183. When the unit is intreatment ready mode, and hence in either tile mode or paint mode, agreen LED 192 above the treatment ready mode button 188, which serves asa treatment ready mode indicator, lights to indicate this condition.Like the master key switch 167, the treatment mode key switch 190requires a key for operation to guard against unauthorized orunintentional changes between the two therapeutic treatment modes.Operation of the system in tile and paint mode is described in moredetail below.

The system 10 described above can be used advantageously to teatpsoriasis in a medical patient by first using the system to determinethat patient's minimal erythema does (MED) and then by deliveringtherapeutic treatment to the patient based on that MED. Use andoperation of the system 10 in such a way is described below for purposesof illustration.

The system 10 is first positioned and plugged into a suitable source ofelectrical power. The master key switch 167 (see FIG. 11) is switchedon, the unit enters the POST mode, and the system 10 begins itsself-test routine as the unit warms up. When the self-tests arecompleted and the unit is fully warmed up, the system 10 enters standbymode, in which it is ready for calibration, if needed.

If calibration is needed, the operator inserts the deliver end 50 (FIG.6) of the wand 32 without any shield 52 (see FIG. 7) into thecalibration port 42 (FIG. 6) on the front side of the UV light source12. The operator must then depress the pushbutton 60 on the wand 32 toopen the path for laser energy to emerge from the wand. The operatorthen depresses the foot pedal 31 and the unit begins lasing. Laserpulses are delivered into the calibration port where the intensity ofthe pulses is measured to determine their power output. The laser'spower is calibrated and adjusted automatically by the system 10 toensure that the wand 32 delivers about fifteen millijoules ofultraviolet energy into the calibration port with each laser pulse. Whencalibration is complete, this will be indicated in the display window162 on the control panel 30 (see FIG. 11), and the system 10 will returnto standby mode.

The system is used in MED mode to determine the patient's individualMED. FIG. 12 depicts a MED template 195, which is a thin, flexibleplastic sheet with six individually numbered MED template apertures 198sized to receive the shield 53 at the delivery end 50 of the wand 32.The MED template 195 further includes marking holes 200 with cross-hairsfor positioning the template on the patient's skin in a suitablelocation. The MED template 195 will be used to determine the patient'sMED and should be taped in place on the patient's skin in an untaggedregion that is not normally exposed to sunlight, e.g., the back,stomach, or buttocks. The location should, moreover, be one that is notaffected by the patient's skin disorder. To facilitate laterrepositioning of the MED template 195 in the same location, thepatient's skin should be marked with a marker through the marking holes200.

With the MED template 195 taped in an appropriate location on thepatient's skin, the operator presses the MED ready mode button 183 toput the system 10 into MED mode. The operator aligns the shield 53 onthe end of the wand 32 with the first MED template aperture 198 of theMED template 195. The soft pads 150 on the nubs 55 at the end of theshield 53 should rest lightly against the patient's skin to ensure thatthe wand 32 is the proper distance from the patient's skin. With thewand 32 properly positioned, the operator depresses the pushbutton 60 onthe wand, and then operators the foot pedal 31 to initiate lasing. Thesystem 10 operates automatically to deliver energy to the patient's skinin an amount equal to 100 millijoules per square centimeter.

The operator then moves the wand 32 to the second MED template aperture198 and, again with the pushbutton 60 held down, operates the foot pedal31. The system 10 adjusts itself automatically in MED mode to deliver anumber of pulses sufficient to deliver 150 millijoules per squarecentimeter to the skin under the second cutout. The operator repeats theprocess with the system automatically adjusting to deliver standard MEDdetermination doses as follows:

MED TEMPLATE APERTURE MED DETERMINATION DOSE NUMBER ENERGY (mJ/cm²) 1100 2 150 3 200 4 250 5 300 6 350

Note that the system 10 increments the MED determination dosesautomatically without further input from the operator. Each MEDdetermination is incremented and delivered in turn. The user need onlyensure that the wand 32 is aligned properly with the appropriate MEDtemplate aperture 198. After the MED determination doses are delivered,the template 195 is removed, and the patient is then asked to return thenext day for observation and determination of that patient's MED.

When the patient returns, preferably, about 24 hours after delivery ofthe MED determination doses, an identical MED template 195 is againplaced over the patient's skin with the help of the marks madepreviously. A patient's MED is defined as the minimal dosage at which anoticeable change in color occurs with distinct edges. The practitionernotes and specifies the patient's MED in terms of the number (1-6) ofthe MED template aperture 198 that corresponds to the lowest MEDdetermination dose for which this distinct color change occurs.

After the patient's MED has been determined the patient's physicianselects a “treatment multiplier.” The system 10 is programmed to accepttreatment multipliers in the form of integer numbers between e.g., twoand eight or two and sixteen or twenty. The inventors have found that atreatment multiplier of two provides mild but nevertheless effectivetherapy, while a treatment multiple of eight provides more aggressiveand generally more effective therapy while still remaining withinacceptable safety limits. Intermediate treatment multipliers produceintermediate effects.

After the patient's MED has been determined and a treatment multiplierchosen, the user may begin delivering therapeutic treatment. The usershould also adjust treatment mode key switch 190 to select between tilemode and paint mode. When the user place the system 10 in treatmentready mode by depressing the treatment ready mode button 188, the system10 will prompt the user to enter the patient's MED and the preselectedtreatment multiplier.

In tile mode, the system 10 will operate automatically to deliver anumber of energy pulses equal to one therapeutic does each time the footpedal 31 is pressed by the user. The therapeutic dose is equal to thepatient's MED, as determined previously, multiplied by the preselectedtreatment multiplier. Thus, for example, if the first color change withdistinct edges was noted corresponding to the third MED templateaperture number, the patient's MED will have been found to be 200millijoules per square centimeter. If a treatment multiplier of six isselected, the system 10 will operator to deliver a number of pulsescorresponding to 1200 millijoules per square centimeter each time thefoot pedal 31 is pressed.

The user will then move the wand 32 stepwise over the patient'spsoriasis, stopping at multiple locations to press the soft pads 150 ofthe shield 53 lightly against the patient's skin. At each location, theuser will operate the foot pedal 31 and pushbutton 60 to deliver onetherapeutic dose before moving on to the next location. The user willrepeat this process until substantially the entire area of the patient'spsoriasis has been treated.

An ink pad 203 bearing a quantity of an appropriate nontoxic ink may beprovided to assist the user in covering the entire treatment surfaceuniformly in tile mode. As depicted in FIG. 13, the shield 53 at the endof the wand 32 may be pressed lightly onto the ink pad so that the softpads 150 at the ends of the shield numbs 55 pick up a small quantity ofthe ink.

As suggested by FIG. 14, when the soft pads 150 are pressed against thepatient's skin, the ink on the soft pads (see, e.g., FIG. 10) will markthe patient's skin at the location of the nubs 55. As described above,the optics of the system 10 are such that the nubs 55 correspond to thecorners of the treated area. The user may the move the wand 32step-wise, aligning the soft pads 150 at a treatment location withcorner marks of a previous location and delivering therapy at eachlocation until substantially the entire area of the patient's affectedskin is treated. FIG. 14 shows corner marks 205 formed by ink from thesoft pads arrayed in a “tile” pattern across the patient's skin over anarea of diseased tissue. When treatment is completed, the user shouldswitch the system 10 to standby mode by pressing the standby button 178on control panel 30.

Paint mode differs from tile mode in that therapy is delivered as thewand 32 is swept more or less continuously over the treated surfacerather than at multiple discrete locations as is the case in tile mode.Paint mode is similar to tile mode in that before initiating treatment,the user will first enter the patient's MED and the preselectedtreatment multiplier as described above.

In paint mode, the user moves the wand 32 over the entire treated areain patterns suggested by FIG. 15. To ensure complete coverage, the userfirst moves the wand 32 in the horizontal pattern 207, the user thenrepeats the motion using the vertical pattern 210. In each pattern, theuser may move the wand 32, for example, at a rate of two squarecentimeters per second. The unit will automatically generate laserpulses at a rate appropriate to deliver the desired therapeutic doseover the course of the two treatment passes.

Test Results

Efficacy of a system 10 and method similar to the one described above intreating psoriasis was evaluated in an investigative clinical trial.Thirteen patients were enrolled in the clinical trail. Each of the trialsubjects had psoriasis manifesting itself in the form of multiple stableplaques. Stable plaques were defined as plaques that had been presentand essentially unchanged for at least eight weeks prior to thepatient's enrollment in the study. Patient's enrolling in the study wererequired to cease all topical therapy for at least two weeks prior totreatment in the study, systemic therapy for at least eight weeks, andphototherapy and photochemotherapy for at least four weeks.

The clinical study was conducted with apparatus 10 substantially thesame as that described above. Each patient's individual minimal erythemadose (MED) was determined by exposing the patient's skin to a set ofcontrolled response calibration doses. The response calibration doseswere applied to unexposed gluetal skin not affected by psoriasis. The UVlight source 20 comprising a laser and the delivery device 15 used inthe study generated a beam of ultraviolet light having a circularcross-section with an area of 4.91 cm² (2.5 cm in diameter). Eachpatient received eight different calibrations doses—100, 140, 280, 400,560, 800, 1120, and 1600 millijoules delivered over the 4.91 cm² area ofthe beam.

The patient's response to the response calibration doses was observed 24hours after the calibration doses were delivered. Each patient'sindividual MED was defined as the minimum calibration does at which acolor change with well defined edges was observed. Individual MEDs weredetermined by observing each patient's unique response to the responsecalibration dose.

After an MED was determined for each patient, a tightly controlled andclosely observed regimen of therapeutic treatments was conducted on thesubjects. Four similarly appearing plaques of adequate size wereselected for each patient. Originally, it was intended that ultravioletlight would be delivered to six different locations on each of the fourplaques in doses equal to 0.5, 1, 2, 4, 8, and 16 times the patient'sindividually determined MED. Thus, it was intended that each patientwould receive therapy at 24 different locations, six locations in eachof four plaques.

All of the plaques were intended to receive identical therapeutic doses.Each plaque, however, was intended to receive therapy according to adifferent treatment schedule. The first plaque would receive a singletreatment, the second plaque two treatments, and the third plaque four.The fourth plaque was to receive 20 treatments. Treatments to the fourthplaque were administered twice weekly with a 72-hour interval betweeneach administration. The 20 twice-weekly treatments were thus given overa 10-week period.

The patient's skin was marked at the time of therapy with indelible inkat each treatment site for subsequent identification. The patients wereobserved and evaluated at 2-week intervals during the 10-week treatmentperiod, and at two, four, and six months after the treatment ended.

When the study began, response calibration doses in the amounts notedabove were administered first to each of the thirteen patients. Thepatients' responses to the calibration doses were observed, andindividual MEDs were determined for each patient. Ultraviolet lightdelivery then began for purposes of therapy. When the first threesubjects were treated, it was observed that dosages of 8 and 16 timesthe patient's MED caused blistering at the treatment site withintwenty-four hours of administration. It was therefore decided that thetreatment regimen should be modified to include delivery doses of 0.5,1, 2, 3, 4, and 6 times the patients' MEDs. These doses were welltolerated by all the subjects, with some slight erythema observed insome subjects at 4 and 6 MEDs. This erythema was occasionallyaccompanied by a moderate burning sensation, in which case treatment atthese doses was temporarily omitted.

Repeated doses at 0.5 and 1 MED did not significantly alleviate thepsoriasis. However, repeated exposures at between 2 and 6 MEDs didresult in significant improvement by approximately 8 weeks following 2treatments, 6 weeks following 4 treatments, and 3-4 weeks with 20treatments. It was noted that after the blistering had healed in thethree patients who received doses of 8 and 16 MEDs, the patient'spsoriasis had cleared at those sites as well.

This method for treating skin disorders including but not limited topsoriasis and vitiligo can be improved by cooling the skin to be treatedprior to and/or during application of high doses of narrow band UV lightto the affected area of the skin. Cooling can be accomplished, e.g., byspraying the skin with a cool liquid, gas, or air or by applying a coolobject to the affected area of skin. Cooling reduces the degree ofinjury to the patient that would ordinarily result from exposure to suchelevated levels of UV light and thus permits higher doses of UV light tobe administered. For example, when a pulsed source such as a pulsedlaser is employed, cooling counters the build up of thermal energy witha series of pulse so that high temperatures associated with injury tothe epidermis are not reached. Cooling may also remove heat, slowing theaccumulation and the rise in temperature with application of theplurality of pulses. Heat can then be dissipated under normal thermaldissipation processes that occur over times exceeding the thermaldissipation time constant τ_(THERMAL). Cooling may also establish a lowtemperature as the starting point from which the skin begins to heat upas thermal energy accumulates with each additional pulse. By preventingtissue damage and thereby enabling higher fluences of UV light, thetotal number of treatments can be reduced and remission can be improved.Cooling can also permit more frequent treatments if necessary. Theaffect of cooling on the skins response to UV light is more fullydescribed in “Influence of Temperature on Ultraviolet Injury” R.Freeman, J. Knox, Arch. of Derm., Vol. 89, June 1964.

To reduce UV damage, the surface of the tissue to be treated ispreferably cooled to about 5° C. or below, and more preferably to about0° C. just prior to and/or during application of the UV radiation. Thegreater the degree of cooling, the higher the tolerance to the dosewithout injury; thus temperatures of about −5° C. or less may improveresults of UV treatment. The low temperature limit is set by the amountof cooling that will damage healthy skin in the proximity of the diseasetissue. At a minimum, the diseased skin must be cooled to a temperaturesubstantially lower than the normal temperature of skin, the normaltemperature of skin being about 34° C.

Cooling can be accomplished by applying a chilled UV transparentsubstrate 2210 such as shown in FIGS. 16-18 to the area of skin to betreated. This cooled substrate or plate 2210 may comprise, e.g.,sapphire, quartz, fused silica, borosilicate glass, or any glass orother material that is transparent to UV light in the preferredwavelength range for treatment and that can withstand the cooling. Tosimplify the treatment procedure for the heathcare provider, this cooledsubstrate 2210 may be incorporated in and connected to a device 2015used to deliver UV radiation from a UV source to a localized region ofskin that includes the diseased tissue. This substrate 2210, forexample, may be attached to a wand 2032 similar to the one depicted inFIGS. 6-10 and having a rectangular output aperture 138 shown in FIGS. 8and 10 at the end 2050 where UV light is emitted for delivery to thepatient. As most clearly shown in FIGS. 17 and 18, the plate 2210 iscircular and has oppositely facing circularly shaped surfaces 2212,2214, one proximal and one distal to the output aperture 138 of the wand2032. The plate 2210, and more particularly, the opposing circularlyshaped surfaces 2212, 2214, have a spatial extent greater in size thanthe rectangular output aperture 138 of the wand 2032 so that lightforming a beam and exiting the output aperture will be fully containedwithin the circular surfaces of the plate as it passes through them. Theplate 2210 is mounted on the shield 2053 such that the distal surface2214 forms an exterior surface of the delivery device 2015 forunrestricted access to the epidermis of the patient; that is, no othersurface on the wand 2032 or device prevents the distal surface fromfully contacting the patient's skin.

A thermoelectric cooler 2216 having a plurality of cooling leads 2218 ismounted on the plate 2210 such that the cooling leads are firmlyconnected to and form good thermal contact with the proximal surface2212 of the plate. Adhering the thermoelectric cooler 2216. to the plate2210, and more particularly to one of the circular surfaces 2212, 2214of the plate, is convenient as both circular surfaces on the plateprovide large areas for accommodating the cooler and its cooling leads2218. Mounting the cooler 2216 on the distal surface 2214 of the plate2210 is less desirable as the distal surface is preferably freed of anyobstructions that would limit good thermal contact between the coolingplate 2210 the patient's skin. Such irregular features on the distalsurface 2214 of the plate 2210 would, in addition, likely inhibitsmoothly scanning this chilled plate across a patient's skin. However,to the extent that such limitations could be avoided, the cooler can belocated on the distal surface 2214 or on other surfaces of the coolingplate and/or of the wand 2032 e.g., on the shield 2053. However, byselecting a location for the cooler 2216 such that a substantial portionof the cooling leads 2218 touch the cooling plate 2210, the coolingplate can be efficiently cooled.

Electrical wires 2220 run through the wand 2032 and to thethermoelectric cooler 2216 to provide electrical power for cooling theleads 2218. These electrical wires 2220 connect to the wand 2032 throughan elastomeric connection boot 2021, which offers strain relief andguards against kinking and which is mounted on the wand 2032 adjacentone other elastomeric connection boot 2057 that receives an opticalcable 2033 for delivery of UV light. A return optical cable is notincluded in this embodiment. The thermoelectric cooler 2216, includingthe cooling leads 2218, and the electrical wires 2220 to the wand 2032can be affixed to the wand 2032 in a conventional manner such as forexample with the aid of an adhesive.

The chilled substrate 2210 is to be employed with the apparatus 1010described above which offers significant advantages in treating skindisorders and which comprises a source 1012 of UV radiation and adelivery system 1014. The chilled substrate 2210, for example, may beused in connection with a laser-based system 1010 such as depicted inFIG. 3 that contains a laser 1020, possible computer controlled, that isoptically coupled to a hand piece 1030 via a flexible guide 1024. Thelaser 1020 may comprise an excimer laser outputting light having awavelength of about 308 nanometers while the hand piece 1030 mightresemble the wand 2032 shown in FIG. 16. In one specific embodiment, thelaser 1020 can be energized for up to 300 pulses in about a second andthe wand 2032 distributes about 10 millijoules per pulse (mJ/pulse)output from the 308 nanometer excimer laser over an area ofapproximately 3 cm² at a target region of the epidermis. The UV beamapplied to the diseased skin is not, however, limited to these specificfluency and size specifications but rather may range widely as describeabove. In particular, an area of skin greater than 3 cm² of skin may becooled to about 0° C. when placed on the skin.

To treat a patient afflicted with a skin disorder responsive to UVlight, the healthcare provider may position the wand 1032 over adiseased region of skin such that a substantial portion of the distalsurface 2214 of the cooled plate 2210 is in physical contact with thediseased region. With the thermoelectric cooler 2216 activated, the areaof skin touching the plate is cooled, preferably to a temperature belowabout 5° C., and more preferably to about 0° C. or less. Light emittedfrom the laser 1020 is coupled via the input cable 2033 into the wand2032 and exits from the wand after passing through the rectangularaperture 138. This light propagates forward within a beam that istransmitted through the chilled plate 2220 and projected onto the skinpressed against the distal end 2214 of the plate. A therapeutic dose ofUV light is thereby directed onto the skin in accordance with thediscussions above with regard to FIGS. 1-15, but while the skin iscooled to a temperature lower than the normal temperature of skin.Substantially all of this dose of ultraviolet light is applied to theskin before the chilled plate warms up, that is, within a period of timeshorter than the thermal time constant associated with the plate 2210.In addition, the dose is preferably, although not necessarily, appliedto only a fraction of the area of skin that is cooled. Likewise, thebeam of light that exits the wand 2032 will likely illuminate only aportion of the chilled plate 2210. For example, in the case of treatingpsoriasis, the beam may encompass both the psoriatic plaque andsurrounding paralesional tissue as well as some adjacent healthy tissue,with both the plaque, the paralesional tissue, and preferably anadditional peripheral region of healthy skin all being cooled.

Other arrangements for cooling the plate or substrate 2210 are includedwithin the scope of the invention. In lieu of mounting a thermoelectriccooler 2216 on the surface 2212 of the plate, the plate 2210 may becooled with fluid by providing a pathway for flowing a liquid or gaschilled to a desirably cool temperature across or through the plate. Forexample, hollow metal lines can be place in thermal contact with thesubstrate 2210 and chilled water can be circulated through these linesto sufficiently lower the temperature of the plate. In addition, theplate 2210 need not be attached to the delivery device 2015 but may beseparate and independent from the delivery device. For example, the UVtransparent plate or substrate 2210 may be cooled in a refrigerator, orby immersing it in or contacting to or otherwise exposing it to achilled liquid, solid, or gas prior to or while being placed on thepatient's skin. The light can then be passed through the chilled plate2210 in a manner described above. Similarly, an object formed into ashape other than a plate but having a temperature less than thetemperature of the diseased skin, and preferably below about 5° C. or 0°C. can be employed to cool the skin and provide therapeutic results. Thecool object need only be transparent to UV light of the wavelengthemployed for treatment and preferably comprise a material suitable formaintaining a cool temperature for a sufficiently long period and thatis thermally conductive so as to readily absorb heat from the skin.

Alternatively, cooling can be accomplished by exposing the skin directlyto chilled liquid or gas or cooled air, possibly in the form of a sprayor stream ejected from jets 2222 incorporated in the wand 2032 depictedin FIG. 19. These jets 2222 are formed by providing openings 2224 inchannels 2226 for flowing liquid or gas coolant or cool air through thewand. In the wand 2032 depicted in FIG. 19, portions of the channels2224 for transporting the coolant are visible adjacent to and in contactwith the UV shield 2053. Other portions of the channels are in interiorregions of the wand 2032 and are thus not visible from the perspectiveshown in FIG. 19. A supply tube 2228 feeds the channels 2226 locatedwithin the wand 2032. This supply tube 2228 is connected to the wand2032 through the elastomeric connection boot 2022 mounted on the wand2032 adjacent another elastomeric connection boot 2057 that receives theoptical cable 2033 for delivery of UV light. As discussed above, theseelastomeric connection boots 2022, 2057 offer strain relief and guardagainst kinking.

The supply tube 2228 is connected at one end to a source of coolant (notshown) comprising, e.g., a supply of chilled coolant or cyrogens, and atanother end to the channels 2224 traversing through the wand 2032. Thesechannels 2224, which may be insulated, provide a pathway for the liquidor gaseous coolant from the supply tube 2228 to the openings 2224 in theportion of the channels located at the delivery end 2050 of the wand2032. These openings 2224 are oriented to direct the spray toward aregion where light from the wand 2032 is also incident. The jets 2222,however, are preferably designed to spread the coolant over an area ofthe patient's skin that is larger than that portion illuminated by thebeam of UV light. The coolant employed may comprise chilled water,chemical solutions sufficiently cooled, liquid or gas cryogens such asfreon, liquid CO₂ or liquid N₂, or combinations thereof. Other possiblecoolants that are suitable for spraying on the patient's skin priorand/or during exposure to UV light include but are not limited to coolair.

Like the chilled substrate 2210, the jet spray is to be employed withthe apparatus 1010 for treating skin disorders described abovecomprising a source of UV radiation 1012 and a delivery system 1014. Thejet spray, for example, may be used in connection with an arc lamp-basedsystem 1010 such as depicted in FIG. 4 and that contains an arc lamp1040 optically coupled to a hand piece 1052 via a flexible guide 1050.The system 1010 additionally includes a filter 1046 for limiting thewavelengths of light to a narrow band of UV preferably somewhere betweenabout 300 and 315 nanometers and a reflector 1042 for collecting lightemitted from the lamp. In one specific embodiment, the lamp-based system1010 produces at least 1 watt (W) of UV radiation that is directed ontothe patient's skin. The lamp 1040 is optically coupled by a lens 1048 tothe UV light guide 1050, which is connected to the handpiece 1052 orwand 2032. A mechanical shutter 97 in the wand 2032 controls the flowthe light output therefrom. This mechanical shutter 97 is connected to amultifunction trigger 2060 which is conveniently located on the wand2032 depicted in FIG. 19 and which, when depressed, opens the shutter.One or more valves (not shown) situated in the channels 2226 may also beelectrically or mechanically connected to the multifunction trigger 2060such that the trigger, when depressed, also opens the valve.

To treat a patient afflicted with a skin disorder responsive to UVlight, the healthcare provider positions the delivery end 2050 of thewand 1032 over a diseased area of skin such that the openings 2224 ofthe jets 2222 are in position to direct coolant onto a portion of skinincluding but not necessarily limited to the diseased area. The operatorthen depresses the trigger 2060 to allow the UV radiation from the lamp1040 to pass through the wand 2032 and onto the patient's skin. The jets2222 are also activated by the trigger 2060 on the wand 2032. Thecoolant flows from reservoir through the supply tube 2228 into thechannels 2226 in the wand 2032 and out the opening 2224 of the jets2222. Preferably, the coolant is pumped through the jets 2222 or thereservoir is a pressurized source of coolant such that the coolant issprayed out of the opening of the jets and spreads onto the skin. Thecoolant spray cools on contact with the skin. Preferably, the spraycools the skin to a temperature below about 5° C., and more preferablyto about 0° C. or less prior to and/or during exposure of the skin to UVlight delivered by the wand 2032. In the case where the coolantcomprises chilled liquid or gas, the low temperature of the coolantcools the skin, however, the coolant may provide additional cooling ifthe coolant evaporates upon or soon after contacting the skin.

In addition, the wand 2032 directs a therapeutic dose of UV light ontothe skin in accordance with the discussions above with regard to FIGS.1-15, however this dose is delivered while the skin is cooled to atemperature lower than the normal temperature of skin, i.e. about 34° C.As described above, the skin is preferably cooled prior to and/or duringUV exposure and substantially all of the dose of UV light is applied tothe skin before the skin warms up. Also, the jet spray preferably coolsthe skin faster than the skin receives the total integrated sum of UVradiation directed to one location. The skin is therefore sufficientlycooled prior to application of injurious doses of radiation to the skin,and thus, tissue damage is avoided or at least minimized. In addition,as previously mentioned, the dose is preferably, although notnecessarily, applied to only a fraction of the area of skin that iscooled.

The technique of providing cooling is not limited to any one particularway of cooling the skin prior to and/or during exposure to suitabledosages of UV light having the appropriate wavelength. Rather, othermethods and apparatus for cooling the plate or substrate 2210 areincluded within the scope of the invention. For example, cool air can beejected from the jets 2222 or supplied by a circulating fan or blower.In addition, in cases, where jets 2222 are employed, the Venturii affectmay be exploited to create a chilled zone. Alternatively, a UVtransparent gel may be applied to the skin; the gel may be cooled beforeor after it is applied to the epidermis to achieve appropriate cooling.This gel may also aid in coupling the UV energy from the source 1012 tothe skin by providing index-matching. In addition, many skin disorderssuch as psoriasis are accompanied by scaling and flaking of the skin.The cooling gel or fluid may also serve to wet this dead skin to allowmore UV light to penetrate instead of being scattered by the scaling,flaking areas of skin.

Selection of the appropriate method of cooling may be influenced by theintended use and the anticipated frequency of use. Systems designed totreat small areas of diseased tissue such as psoriasis plaque modest insize, may suitably employ a cryogen spray, which is consumable. Incontrast, a liquid cooled window with a recirculating chiller may bemore appropriate for treating larger areas of skin afflicted by, e.g.,vitiligo or psoriasis, as fast and effective cooling can be providedwithout requiring a large supply of a consumable coolant.

As described above, cooling the skin increases the skin's tolerance tohigh doses of UV light. Higher doses of UV light can be applied to theskin without inducing tissue damage. With higher doses of UV light, thetotal number of treatments can be reduced, thereby lowering the cost oftreating the skin disorder. Requiring less doctor visits also promotespatient compliance to an otherwise difficult regimen and improves thelikelihood of success of the overall treatment.

Cooling also permits a higher frequency of individual treatmentsessions. A typical treatment regimen may include three or more visitsto the physician or healthcare provider to completely clear the disease.In an effort to avoid injury, a subsequent session is not scheduled toosoon as time is necessary to permit healing. Consecutive sessions, forexample, should be separated by at least about 90 hours when suitabledoses of 308 nanometer light are employed to treat the disease. The timebetween sessions, however, can be shortened by cooling the skin prior toand/or during the application of UV light as discussed above, i.e., ifthe skin is cooled during exposure to ultraviolet light, a subsequenttreatment session can follow sooner. For these and other reasons, the UVtreatment preferably includes cooling.

Thus, is has been demonstrated that psoriasis can be treated effectivelyby local administration of ultraviolet light in high doses. Since thepatient's tolerance of and response to ultraviolet therapy variessignificantly according to their individual skin types, it is highlyadvantageous to administer the therapy based on observed individual MEDsdetermined for each patient.

The therapy should be delivered at greater than one times the patient'sMED per treatment. More preferably, the therapy should be delivered indoses of between 2 and 6 MEDs per treatment. Therapy may be delivered ina single treatment, but multiple treatments may be preferred. Treatmentmay be delivered once, twice or four times. Treatment may also bedelivered twice per week for ten weeks in succession. Cooling the skinprior to and/or while exposing the skin to the UV light can permithigher doses to be used thereby reducing the total number of individualtreatment sessions. Cooling can also shorten the time between successivetreatment sessions.

A preferred system 10 and methods for delivering phototherapy accordingto the invention has been described herein. Modifications and additionsto this preferred method will no doubt occur to those skilled in theart. For example, although the method has been described as suitable fortreatment of psoriasis, the method is not so limited, but rather may beeffective in treating many other skin diseases as well. Furtherapplications, additions and modifications may occur to those skilled inthe art and the scope of the invention is not to be limited to thepreferred embodiment described herein. Rather, the scope of theinvention should be determined by reference to the following claims,along with the full scope of equivalents to which those claims arelegally entitled.

1. A method for treating an epidermal region comprising diseased tissue,the method comprising: cooling the diseased tissue to below about 0° C.and exposing the diseased tissue in said epidermal region to a dosage ofultraviolet light between about 16 and 20 minimum erythema doses (MED)in the wavelength range of between about 300 and 315 nanometers.
 2. Themethod of claim 1, wherein the epidermal region exposed to ultraviolethas an area between about 1 cm² and about 4 cm².
 3. The method of claim1, wherein cooling comprises spraying the skin with a cool liquid, gas,or air.
 4. The method of claim 1, wherein cooling comprise contactingthe diseased tissue with a chilled surface.
 5. The method of claim 1,wherein the diseased tissue is cooled to below about −5° C.
 6. Themethod of claim 1, further comprising determining the MED of a patienthaving said epidermal tissue.